#!/usr/bin/env python
# Copyright 2019 The Pigweed Authors
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may not
# use this file except in compliance with the License. You may obtain a copy of
# the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations under
# the License.
"""Installs and then runs cipd.

This script installs cipd in ./tools/ (if necessary) and then executes it,
passing through all arguments.

Must be tested with Python 2 and Python 3.
"""

from __future__ import print_function

import hashlib
import os
import platform
import subprocess
import sys

try:
    import httplib
except ImportError:
    import http.client as httplib

try:
    import urlparse  # Python 2.
except ImportError:
    import urllib.parse as urlparse

SCRIPT_DIR = os.path.dirname(__file__)
VERSION_FILE = os.path.join(SCRIPT_DIR, '.cipd_version')
DIGESTS_FILE = VERSION_FILE + '.digests'
# Put CIPD client in tools so that users can easily get it in their PATH.
CIPD_HOST = 'chrome-infra-packages.appspot.com'

# Get install dir from environment since args cannot be passed through this
# script (args are passed as-is to cipd).
INSTALL_DIR = os.environ.get('CIPD_PY_INSTALL_DIR',
                             os.path.join(SCRIPT_DIR, 'tools'))
CLIENT = os.path.join(INSTALL_DIR, 'cipd')


def platform_normalized():
    """Normalize platform into format expected in CIPD paths."""

    try:
        os_name = platform.system().lower()
        return {
            'linux': 'linux',
            'mac': 'mac',
            'darwin': 'mac',
            'windows': 'windows',
        }[os_name]
    except KeyError:
        raise Exception('unrecognized os: {}'.format(os_name))


def arch_normalized():
    """Normalize arch into format expected in CIPD paths."""

    machine = platform.machine()
    if machine.startswith('arm'):
        return machine
    if machine.endswith('64'):
        return 'amd64'
    if machine.endswith('86'):
        return '386'
    raise Exception('unrecognized arch: {}'.format(machine))


def user_agent():
    """Generate a user-agent based on the project name and current hash."""

    try:
        rev = subprocess.check_output(
            ['git', '-C', SCRIPT_DIR, 'rev-parse', 'HEAD']).strip()
    except subprocess.CalledProcessError:
        rev = '???'
    return 'pigweed-infra/tools/{}'.format(rev)


def actual_hash(path):
    """Hash the file at path and return it."""

    hasher = hashlib.sha256()
    with open(path, 'rb') as ins:
        hasher.update(ins.read())
    return hasher.hexdigest()


def expected_hash():
    """Pulls expected hash from digests file."""

    expected_plat = '{}-{}'.format(platform_normalized(), arch_normalized())

    with open(DIGESTS_FILE, 'r') as ins:
        for line in ins:
            line = line.strip()
            if line.startswith('#') or not line:
                continue
            plat, hashtype, hashval = line.split()
            if (hashtype == 'sha256' and plat == expected_plat):
                return hashval
    raise Exception('platform {} not in {}'.format(expected_plat,
                                                   DIGESTS_FILE))


def client_bytes():
    """Pull down the CIPD client and return it as a bytes object.

    Often CIPD_HOST returns a 302 FOUND with a pointer to
    storage.googleapis.com, so this needs to handle redirects, but it
    shouldn't require the initial response to be a redirect either.
    """

    with open(VERSION_FILE, 'r') as ins:
        version = ins.read().strip()

    try:
        conn = httplib.HTTPSConnection(CIPD_HOST)
    except AttributeError:
        print('=' * 70)
        print('''
It looks like this version of Python does not support SSL. This is common
when using Homebrew. If using Homebrew please run the following commands.
If not using Homebrew check how your version of Python was built.

brew install openssl  # Probably already installed, but good to confirm.
brew uninstall python && brew install python
'''.strip())
        print('=' * 70)
        raise

    path = '/client?platform={platform}-{arch}&version={version}'.format(
        platform=platform_normalized(),
        arch=arch_normalized(),
        version=version)

    for _ in range(10):
        conn.request('GET', path)
        res = conn.getresponse()
        # Have to read the response before making a new request, so make sure
        # we always read it.
        content = res.read()

        # Found client bytes.
        if res.status == httplib.OK:  # pylint: disable=no-else-return
            return content

        # Redirecting to another location.
        elif res.status == httplib.FOUND:
            location = res.getheader('location')
            url = urlparse.urlparse(location)
            if url.netloc != conn.host:
                conn = httplib.HTTPSConnection(url.netloc)
            path = '{}?{}'.format(url.path, url.query)

        # Some kind of error in this response.
        else:
            break

    raise Exception('failed to download client')


def bootstrap():
    """Bootstrap cipd client installation."""

    client_dir = os.path.dirname(CLIENT)
    if not os.path.isdir(client_dir):
        os.makedirs(client_dir)

    print('Bootstrapping cipd client for {}-{}'.format(platform_normalized(),
                                                       arch_normalized()))
    tmp_path = os.path.join(INSTALL_DIR, '.cipd.tmp')
    with open(tmp_path, 'wb') as tmp:
        tmp.write(client_bytes())

    expected = expected_hash()
    actual = actual_hash(tmp_path)

    if expected != actual:
        raise Exception('digest of downloaded CIPD client is incorrect, '
                        'check that digests file is current')

    os.chmod(tmp_path, 0o755)
    os.rename(tmp_path, CLIENT)


def selfupdate():
    """Update cipd client."""

    cmd = [
        CLIENT,
        'selfupdate',
        '-version-file', VERSION_FILE,
        '-service-url', 'https://{}'.format(CIPD_HOST),
    ]  # yapf: disable
    subprocess.check_call(cmd)


def init():
    """Install/update cipd client."""

    os.environ['CIPD_HTTP_USER_AGENT_PREFIX'] = user_agent()

    try:
        if not os.path.isfile(CLIENT):
            bootstrap()

        try:
            selfupdate()
        except subprocess.CalledProcessError:
            print('CIPD selfupdate failed. Bootstrapping then retrying...',
                  file=sys.stderr)
            bootstrap()
            selfupdate()

    except Exception:
        print('Failed to initialize CIPD. Run '
              '`CIPD_HTTP_USER_AGENT_PREFIX={user_agent}/manual {client} '
              "selfupdate -version-file '{version_file}'` "
              'to diagnose if this is persistent.'.format(
                  user_agent=user_agent(),
                  client=CLIENT,
                  version_file=VERSION_FILE,
              ),
              file=sys.stderr)
        raise


if __name__ == '__main__':
    init()
    subprocess.check_call([CLIENT] + sys.argv[1:])